THE SCISSOES-BILL. 



303 



kered or Marsh. Tern {Sterna leucupareia) , the Gull-billed Tern 

 (Sterna anglica), the Roseate Tern {Sterna Dougalli), the Sandwich 

 Tern (Sterna cautiaca), and the Tschegruna, or Caspian Tern 

 {Sterna caspica), all of which either breed upon the British coast, 

 or are freq^uent visitors there, although they rarely reach France. 



The Scissors-bills, ok Sea Skimmers {Bynchops, Linn.). 

 The Scissors-bills have received their name from the conforma- 

 tion of their beaks, which are flattened laterally into two laniinaj 

 fitting one on the other, forming two mandibles compressed into 



Fig. 1(j7.— The Eitick Soidaura-bill i^liyiickujj^ nigra]. 



cutting blades, the upper being one-third shorter than the lower. 

 In order to pick up the shrimps and small fishes on which thej^ 

 feed, these birds are obliged to skim the surface of the water, 

 dipping the lower mandible of their bill, the upper mandible being 

 kept ojDen and clear of the water till aquatic insects or other small 

 fry have entered into the lower portion of it.* The singular form 

 of their bills is also of service to them in opening such bivalve 

 shell-fish as come in their way. They frequentlj^ watch these 

 moUusks, and when they notice that the shell of the latter 



* Catesby says : " These bii'ds frequent near the sea-coasts of Carolina. They 

 fly close to the surface of the water, from which they seem to receive somewhat of 

 food." 



